“What's all that racket?”
You're in the kitchen. You hear some loud noise from another part of your house, where your kids are playing with their friends. You want to know what the noise was, so you call out this.
What's all that racket?
When someone is causing a loud or annoying noise, and you want to know why, ask "What's all that ___?" For example:
What's all that yelling?
Hey! What's all that noise?
What's all that banging?
"Racket" is a word for loud and annoying noises. Loud music, shouting, banging noises, and other noises can all be called "racket".
When children make noises that annoy their parents, the parents use the phrase "that racket":
Turn down that racket!
Hey! Stop all that racket!